vibrating prop woes

[Alistair]

so, my 318is.
I had a bit of a vibration - realized i'd misaligned the prop one day changing the fuel tank.
Realigned - less of a vibration.
Thinking i'd stuffed the centre bearing - changed it, pre loaded it and removed the vibration damber (after reading it was not necessary).
Massive vibration - put the vibration damper back on,
changed guibo (which has no arrows ?!?) Vibration worst between 40 and 60mph. I have new gearbox rubbers on the way.
I've spent more time lying under the car than i have in bed,
i'm ready to set fire to it.

am I just a bit simple, or should I give up the spanners?

[bmw9818]

when you remove its best to tippex it across so you know how it aligns, i think you can get it rebalanced?

[Grrrmachine]

One of the basic clues is that the "flats" of the universal joints should be on the same plane, so there's only four possible ways to put the two halves of the prop together.

[Alistair]

yeah the dots and UJ's line up

[Alistair]

oh, and there's no movement from the centreing sleeve

[Billwill]

Strange that there are no arrows on the Guibo....how did you end up aligning the nuts and bolts?

[Brianmoooore]

Vibration at 40 -60 MPH is usually wheel related, as this is the range of speed where one turn of a wheel matches the resonant frequency of the suspension.

[Alistair]

Billwill, from seeing many pictures of props, I think I did bolts on the flange - nuts on the guibo.
what worries me is if the guibo's loaded wrong it wont last long (I bought it so long ago, its was probably a cheap piece of crap anyway)

Thanks Brian, I've seen you write that a few times in my searches.
I didn't have as bad a vibration as I do now before I started screwing with things.
I've been through a few set of tyres, so they get periodically changed and balanced.
I've finally got my self some BBS's so I'll get them on pretty soon, and I hope your right.
would I feel that through the steering wheel as well?

[Duke137]

Billwill, from seeing many pictures of props, I think I did bolts on the flange - nuts on the guibo.
what worries me is if the guibo's loaded wrong it wont last long (I bought it so long ago, its was probably a cheap piece of crap anyway)

Thanks Brian, I've seen you write that a few times in my searches.
I didn't have as bad a vibration as I do now before I started screwing with things.
I've been through a few set of tyres, so they get periodically changed and balanced.
I've finally got my self some BBS's so I'll get them on pretty soon, and I hope your right.
would I feel that through the steering wheel as well?

If a wheel is out of balance, definately.

[Z3I]

If you dont have any steering wheel wobble, change the front wheels to the back, see if that can readuce the vibration, or give you bad steering wobble. Either way, its a clue to whether its wheel related??

[Alistair]

I'll try swapping the wheels when it stops raining, that could be a while.

I feel the vibration through the seat, and its only really been proper
since I changed the prop centre bearing and removed the vibration damper.
I've put the damper back on, and it has "dampened the vibration", but not by much.
As I've read I shouldn't really need it. should I?

I think I'll try getting the prop balanced as well.

[TPS]

Vibration at 40 -60 MPH is usually wheel related, as this is the range of speed where one turn of a wheel matches the resonant frequency of the suspension.

Mine Vibrates between 60-80 MPH (2.5-3.5 RPM), any ideas what this might be Brian?

[G-Bear]

Vibration at 40 -60 MPH is usually wheel related, as this is the range of speed where one turn of a wheel matches the resonant frequency of the suspension.

Mine Vibrates between 60-80 MPH (2.5-3.5 RPM), any ideas what this might be Brian?

I had similar, more of a pulsating vibration. It went when I put new tyres on..

[HairyScreech]

Vibration at 40 -60 MPH is usually wheel related, as this is the range of speed where one turn of a wheel matches the resonant frequency of the suspension.

Mine Vibrates between 60-80 MPH (2.5-3.5 RPM), any ideas what this might be Brian?

Ditto. I think its due to the same thing but with stiffer springs thrown in (raises sus frequency).

The real question with any odd vibration is is it related to engine speed or road speed?

Does changing gear change the vibration?

If not then it is certainly something after the gearbox output, ie, prop, wheels discs etc.

[TPS]

New Discs & pads all round, fitted the other week, along with Lemforder Wishbones & M3 offset bushes

It goes if you change down from 5th to 4th, it goes, when your change back up, it doesn't come back.

Had all the balancing/alignment/tracking done on Saturday, it has 2 new Toyos on it, & 2 Kumho's fitted about a year ago.

Prop. has been taken off & inspected, new Guibo as well.

[HairyScreech]

worn half shaft joint throwing the shaft out off center?

[TPS]

Worn Driveshaft, you mean?

[Brianmoooore]

The front of the prop has a spigot that fits into a bush in the end of the gearbox output shaft. The condition of this bush is often overlooked.

[TPS]

Thanks Brian, is 18/19 in this picture?

http://www.realoem.com/bmw/showparts.do ... g=23&fg=15

And/or no.1 is this one?

http://www.realoem.com/bmw/showparts.do ... g=26&fg=10

[Brianmoooore]

#1 in the second link is the one that can wear. I've got it the wrong way around in my last post - spigot is on the gearbox, and bush is in the prop.

[TPS]

The output shaft was shiny, when the guibo was replaced, wheter that means that bush is knackered, I'll get it replaced, & report back.

[Brianmoooore]

Doesn't need replacing if it's good, which means a good tight fit on the spigot. You should be able to tell if you remove three of the guibo bolts, and see if there's any sideways movement when you push and pull the front end of the prop.